1. Field of the Invention
This invention relates to a server for transmitting moving picture files and to a method of controlling operation of the server.
2. Description of the Related Art
A moving picture transmitting service for a client terminal typified by a mobile telephone has been announced. In the transmission of moving pictures oriented toward mobile telephones, the MPEG4 (Moving Picture Experts Group Phase 4) format is employed for video and the AAC (Advanced Audio Coding) format and AMR (Adaptive Multi-Rate CODEC), etc., are employed for audio. Further, a plurality of formats such as 3GPP (3rd Generation Partnership Project) and 3GPP2, etc., are employed as multiplexed file formats. In addition, there are also instances where a format unique to the mobile telephone carrier is utilized.
It is required that the client terminal to which a transmission is to be made be sent a moving picture file having a format, etc., that is displayable on the client terminal. Since moving picture files have a number of forms and formats, generating the moving picture files beforehand for every model of client terminal requires the preparation of a very large number of types of moving picture files. Generating beforehand a moving picture file that is suitable for display on a client terminal means that a large memory area is required in order to store the moving picture file. Further, generating a moving picture file suitable for display on a client terminal in response to a request from this client terminal necessitates considerable time before the moving picture file can be transmitted to the client terminal.
A number of proposals have been made to deal with these issues. According to Japanese Patent Application Laid-Open No. 9-298749, a moving picture for transmission is expanded up to an intermediate state, the network load is sensed and the moving picture for transmission is generated upon deciding the amount of coding of the moving picture. According to Japanese Patent Application Laid-Open No. 2002-82861, the image compression format, image size and quality are decided by user designation and then the transmission to the user is made. According to Japanese Patent Application Laid-Open No. 2004-88500, moving picture formats of a plurality of types are supported and a moving picture is converted to the format that conforms to the scheme of the transmitting means at the destination of the transmission. According to Japanese Patent Application Laid-Open No. 2004-222124, the model of a client terminal is discriminated, moving-picture generation parameters conforming to the model are decided and a moving picture for transmission is generated. According to Japanese Patent Application Laid-Open No. 2006-343830, a format conversion is made in accordance with attribute data of a client terminal and the picture is then transmitted to the client terminal.
Nevertheless, the time it takes to transmit a moving picture file to a client terminal cannot be shortened while at the same time keeping as small as possible the memory area in which the moving picture file is stored.